spar3d/models/tokenizers/triplane.py

import math
from dataclasses import dataclass

import torch
import torch.nn as nn
from einops import rearrange, repeat
from jaxtyping import Float
from torch import Tensor

from spar3d.models.utils import BaseModule


class TriplaneLearnablePositionalEmbedding(BaseModule):
    @dataclass
    class Config(BaseModule.Config):
        plane_size: int = 96
        num_channels: int = 1024

    cfg: Config

    def configure(self) -> None:
        self.embeddings = nn.Parameter(
            torch.randn(
                (3, self.cfg.num_channels, self.cfg.plane_size, self.cfg.plane_size),
                dtype=torch.float32,
            )
            * 1
            / math.sqrt(self.cfg.num_channels)
        )

    def forward(self, batch_size: int) -> Float[Tensor, "B Ct Nt"]:
        return rearrange(
            repeat(self.embeddings, "Np Ct Hp Wp -> B Np Ct Hp Wp", B=batch_size),
            "B Np Ct Hp Wp -> B Ct (Np Hp Wp)",
        )

    def detokenize(
        self, tokens: Float[Tensor, "B Ct Nt"]
    ) -> Float[Tensor, "B 3 Ct Hp Wp"]:
        batch_size, Ct, Nt = tokens.shape
        assert Nt == self.cfg.plane_size**2 * 3
        assert Ct == self.cfg.num_channels
        return rearrange(
            tokens,
            "B Ct (Np Hp Wp) -> B Np Ct Hp Wp",
            Np=3,
            Hp=self.cfg.plane_size,
            Wp=self.cfg.plane_size,
        )